From: Ryan Roberts ryan.roberts@arm.com
commit c11d34fa139e4b0fb4249a30f37b178353533fa1 upstream.
It is racy to non-atomically read a pte, then clear the young bit, then write it back as this could discard dirty information. Further, it is bad practice to directly set a pte entry within a table. Instead clearing young must go through the arch-provided helper, ptep_test_and_clear_young() to ensure it is modified atomically and to give the arch code visibility and allow it to check (and potentially modify) the operation.
Link: https://lkml.kernel.org/r/20230602092949.545577-3-ryan.roberts@arm.com Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces"). Signed-off-by: Ryan Roberts ryan.roberts@arm.com Reviewed-by: Zi Yan ziy@nvidia.com Reviewed-by: SeongJae Park sj@kernel.org Reviewed-by: Mike Rapoport (IBM) rppt@kernel.org Cc: Christoph Hellwig hch@lst.de Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Lorenzo Stoakes lstoakes@gmail.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Uladzislau Rezki (Sony) urezki@gmail.com Cc: Yu Zhao yuzhao@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: SeongJae Park sj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/damon/vaddr.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-)
--- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -393,7 +393,7 @@ static struct page *damon_get_page(unsig return page; }
-static void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, +static void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr) { bool referenced = false; @@ -402,13 +402,11 @@ static void damon_ptep_mkold(pte_t *pte, if (!page) return;
- if (pte_young(*pte)) { + if (ptep_test_and_clear_young(vma, addr, pte)) referenced = true; - *pte = pte_mkold(*pte); - }
#ifdef CONFIG_MMU_NOTIFIER - if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE)) + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE)) referenced = true; #endif /* CONFIG_MMU_NOTIFIER */
@@ -419,7 +417,7 @@ static void damon_ptep_mkold(pte_t *pte, put_page(page); }
-static void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, +static void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE @@ -429,13 +427,11 @@ static void damon_pmdp_mkold(pmd_t *pmd, if (!page) return;
- if (pmd_young(*pmd)) { + if (pmdp_test_and_clear_young(vma, addr, pmd)) referenced = true; - *pmd = pmd_mkold(*pmd); - }
#ifdef CONFIG_MMU_NOTIFIER - if (mmu_notifier_clear_young(mm, addr, + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + ((1UL) << HPAGE_PMD_SHIFT))) referenced = true; #endif /* CONFIG_MMU_NOTIFIER */ @@ -462,7 +458,7 @@ static int damon_mkold_pmd_entry(pmd_t * }
if (pmd_huge(*pmd)) { - damon_pmdp_mkold(pmd, walk->mm, addr); + damon_pmdp_mkold(pmd, walk->vma, addr); spin_unlock(ptl); return 0; } @@ -474,7 +470,7 @@ static int damon_mkold_pmd_entry(pmd_t * pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); if (!pte_present(*pte)) goto out; - damon_ptep_mkold(pte, walk->mm, addr); + damon_ptep_mkold(pte, walk->vma, addr); out: pte_unmap_unlock(pte, ptl); return 0;